Electrical switches are used to switch electrical currents. One type of electrical switches are so-called circuit breakers, which can typically switch currents of 100 A and more. Circuit breakers are typically accommodated in a housing. The individual phases of the currents are typically switched in so-called switchgear units. To this end, a switchgear unit includes a housing, in which a moving contact and a fixed contact are accommodated, which can be mechanically separated and/or brought together in order to switch the currents off and/or on.
When separating the movement and fixed contact of a switchgear unit, an electric arc is produced which is cancelled out in a so-called arc chamber. The electric arc ionizes the gas of the arc chamber and generates an overpressure in the arc chamber. The arc chamber pressure is equivalent to the electric arc energy. On account of the overpressure, the hot gases flow out of the arc chamber through blow-out channels provided therefor.
It is known to use circuit breakers in power distribution and to allow this to be selectively switched off in the event of a short circuit. This is understood to mean that upstream circuit breakers only then trip if no downstream circuit breaker is able to separate the branch affected by the short-circuit. So-called selective tripping devices are used for selective shut-down.
From a specific tripping limit, the circuit breaker should be switched off by way of the selective tripping device. By way of example, known selective tripping devices use the gas pressure prevailing in the arc chamber during switching processes or they initiate a tripping by way of the magnetic powers prevailing in the event of a short-circuit. In order to open the electrical contacts of the circuit breaker, the selective tripping device actuates the switching lock. In order to trip the switching lock, a specific minimal power is needed which is to be applied. In order to apply this power, selective tripping devices typically have a power-magnifying mechanism.